Apron for digging and carrying scraper and actuating mechanism therefor



pt. 25, 1956 w. J. ADAMS 2,763,942

APRoN FOR DIGGING AND CARRHNG SCRAPER AND ACTUATING MECHANISM THEREFOR Original Filed Aug. 20', 1949 4 Sheets-Sheet 1 INVEN TOR. VVf/.L/A/v e7' Ama/"1.5

l BY A f1 TTORN/Ey Sept. 25, 1956 w J ADAMS 2,763,942

APRON FOR DIGGINE; ND CARRYING SCRAPER AND ACTUATING MECHANISM THEREFOR Qx'ignal- Filed Aug. 20, 1949 4 Sheets-Sham: 2

YANK

IN VEN TOR. WML/AM J' ,40m/m Sept. 25, 1956 w. J. ADAMS 2,763,942 APRoN FOR DIGGING AND CARRHNG scRAPER AND ACTUATING MECHANISM THEREFOR Original Filed Aug. 20, 1949 4 Sheets-Sheet 3 INVENTOR. WILL/AM' J' A0A ms Sept. 25, 1956 w. J. ADAMS 2,763,942

APRoN FOR DIGGING AND CARRYING scRAPER AND ACTUATING MECHANISM THEREFOR Original Filed Aug. 20, 1949 4 Sheets-Sheet 4 rfa/mens United States Patent O APRON FOR DIGGING AND CARRYING SCRAP- ER AND ACTUATING MECHANISM THEREFOR William J. Adams, Santa Cruz, Calif., assignor, by mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware Original application August 20, 1949, Serial No. 111,496. Divided and this application January 20, 1951, Serial No. 206,987

4 Claims. (Cl. 37-126) This invention relates to improvements in a power scraper adapted to dig up and carry away large quantities of earth or similar material in a bowl having an open front end closed by an apron or front gate, and more particularly to an improved apron or gate and actuating mechanism therefor.

This application is a division of my copending application Serial No. 111,496, led August 20, 1949, now Patent No. 2,674,815.

One of `the objects of the present invention is to provide a front gate with a very high lift and wherein the front gate and ejector are so constructed and arranged .that lthey nest within each other at their fully raised position so as to obtain the maximum dumping efficiency.

A further object of my invention is the connection of a pull yoke between a tractor and the scraper bowl and the mounting of the lifting device for the front apron or gate on the pull yoke whereby the lifting movement of the pull yoke is added to the lifting motion of the front apron actuating device to provide a very high lift for the front apron during dumping.

Still another object of the presen-t invention is to provide novel hydraulic hoist operating means for the bowl and the front gate of the scraper mounted on the pull yoke in a novel manner.

A further feature of the present invention is the provision of a novel plural sheave arrangement connected with the hydraulic hoist mounted on the pull yoke so as to multiply the power of the hydraulic hoist as applied to the lifting of the bowl and the lifting of the front apron.

A further object of the present invention is `the provision of powerful hydraulic hoists for power and the application of that power by means of exible cables to the front portion of the scraper bowl and to the front apron of the scraper so as to permi-t both the bowl and the apron to lloat in a desirable manner without cable interference.

A further object of the present invention is to provide a scraper of very strong construction. wherein the sides of the scraper bowl, the ejector and the front gate, and the rear frame and pull yoke are of strongly reinforced construction so that the scraper is very sturdy and rugged.

Other objects and advantages of the present invention will be apparent from the accompanying drawings and description and the essential features `thereof will be set forth in the appended claims.

In `the drawings, Fig. l is a side elevational view of a scraper equipped with my various inventions and showing a rear portion of the tractor which pulls the` same;

Fig. 2 is a fragmental top plan View of the scraper of Fig. l;

Fig. 3 is a longitudinally extending sectional View taken generally along the line 3 3 of Fig. 2;

Fig. 4 is a diagrammatic view illustrating the hydraulic system for operating the various hydraulic hoists;

Fig. 5 is a fragmental sectional view enlarged taken along the line 5-5 of Fig l;

ICC

Fig. 6 is a diagrammatic view illustrating the receiving of the cables on the hydraulic hoists mounted on the pull yoke and connections of these cables to the scraper bowl and the scraper fron-t apron; while Fig. 7 is a diagrammatic view showing the reaving of cable 95.

In Figs. l, 2 and 3, I have shown a. scraper bowl 10 comprising two vertically extending parallel side plates 11 rigidly connected together by a box beam construction 12 at the front end, by upper and lower laterally extending box beams 13 and 14 respectively at the rear, and by a triangularly shaped box beam 15 at the mid portion of the bottom of the side walls just to the rear of the cutting blade 16 which is rigidly mounted on the box beam 15. The side plates 11 are entirely flat and unobstructed on their inner side as shown in Figs. 2 and 3. They are reinforced on their outer surfaces by means of the vertically extending channels 17 and 18 and by the horizontally extending channels 19, 2li and 21. These channels numbered 17 to 21 have the free edges of their flanges welded to the outer face of the plate 11 so that the webs of the channels are spaced from and parallel to the plates 11 giving, in effect, box meams at each of these channel connections. Rearwardly of the box beam 15, `the bottom of the scraper bowl is provided by the bottom portion 22a of the ejector which is con tinuously connected by a curved portion with an upwardly and rearwardly Haring back wall portion 22b which is an integral part of the ejector. The ejector is comprised of two parallel plates 23 which are welded to crosswise extending spacers 24 and parallel stiffening ribs 25. The side edges of the ejector which are closely parallel to the inner faces of the scraper bowl side plates 11, are closed by plates 26 which are welded to the plates 23. This gives a very strong construction for the ejector. The ejector is pivotally mounted by the hinge 27 on the top or apex portion of the triangular box beam 15 as clearly shown in Figs. 2 and 3. The box beam 13 may have an extending skirt 13a extending downwardly to substantially meet the upper edge of the ejector portion 22]) when the scraper bowl is in` its till position. as shown in Fig. l. To hold a greater load, an extension wall may be provided vertically above the box beam 13 and comprising a vertically extending plate 28 which extends across the entire width of the bowl and which is reinforced by a plurality of parallel ribs 29 which are welded to the plate 28 and to the top of the box beam 13.

The rear support for the scraper bowl is very strongly constructed. Two box beams 3) are rigidly connected as by welding to the rear face of the box beam `13 at points inwardly from the side plates 11 of the bowl. These beams 30 extend rearwandly and downwardly to a bumper 31'. Vertically below each of the beams 30 is a beam 31. These beams are also welded to the rear face of the box beam 14 and extend generally horizontally, tapering inwardly toward each other to the bumper 31. The four beams 30 and 31 are welded together to the bumper 31 against which a pusher tractor or bulldozer may exert its pushing effort when aiding the loading of the scraper or moving the scraper forward by additional power. A hook 32 may be provided at this point in case the scraper is used to pull a following vehicle. Approximately midway between the bumper 31 andthe rear of the scraper bowl, the beams 30 and 31 are reinforced by means of upper and lower box beams 33 and 34 respectively which are welded between their associated beams, namely, the beam 33 connecting the beams 30 and the beam 34 connecting the beams 31. Two vertically extending box beams 35 at the opposite ends of beams 33 and 34 provide vertical struts. Each beam 35 extends between the beam 30 and the beam 31 on the same side of the vehicle. Stub axles 36 are mounted in beams 3S and on these are mounted the rear scraper' wheels 37. Preferably, a strut 38 vis mounted between the mid portion of beam 13 and the mid portion of beam 33 as shown in Figs. l and 3. This beam is omitted from Fig. 2 so as to permit the showing of the ejector operating hoist. `A beam 38 is positioned under each beam 30 and extends from beam 13 to beam 34.

The support for the scraper at the front end is provided by means of a pull yoke 39 which is connected by means of a hitch 40 with a four wheel tractor, of which two parallel rear wheels 41 are shown mounted on an axle housing 42. It lshould be understood that this tractor is of the four wheel type Vhaving two wheels forwardly of and generally in front-to-rear alignment with Vthe wheels 41 and provided with an engine at the front connected by the usual change speed mechanism and drive mechanism with the axle for driving the wheels 41. The hitch 40 comprises a horizontaly extending pivot 43 extending crosswise of the vehicle and mounted on a bracket 44 rigid with the axle housing 42. A bracket 4S which pivots on the pin 43 is connected by horizontally extending pin 46 with a bifurcated bracket 47. The pin 46 extends in a fore and aft direction. The bracket 47 carries a vertically extending pin 47a which is embraced by a sleeve 48 which is oscillatable about `the pin 47a. Rigidly welded to the sleeve 48 are two goose neck shaped box beams 49 which diverge rearwardly from the sleeve 48 and have their rear ends rigidly welded to a torque tube 50 which extends crosswise of the vehicle. At opposite ends of the torque tube are rigidly welded the yoke arms `51 which extend rearwardly outside of and parallel to the side plates 11 of the scraper. Each of the arms 51 is of hollow box beam construction. The rear end of each arm S1 is pivotally connected by a hinge pin 52 with the scraper bowl. The pins 52 on opposite `sides of the bowl are axially aligned.

wIt will be noted that the hinge pin connection 52 of the Ypull yoke to the scraper bowl is located above and slightly to the rear of the hinge 27 which is just back of the scraper blade '16. It will -be noted .that the pivot 52 is approximately two-fifths of the distance from the bottom of the bowl to the top and this location has important etects in the practical use of the scraper as will later appear.

The front gate or apronw53 is shown in its closed or lowered position in Fig. l and in its uppermost .raised position in Fig. 3. ThisV gate is made up of parallel plates '54 between which are welded spacers 55 and reinforcing ribs 56. The plates 54 are welded along their-opposite parallel fore and aft extending sides to vertically extending plates 57 which are positioned parallel to andV just inside of the side bowl plates 11. At 4its upper end, each plate 57 is welded to a short cylinder 58 which extends over the side plate 11 of the bowl. To the outside of each of the cylinders 58 is welded an arm 59 which is'just on the outside of and parallel tothe bowl plate 11. It will be noted that the bowlplates 11 are clear and freeof all exterior stifiening ribs at the zone traversed by the arms 59 from the position of Figfl to theposition of Fig. 3 so as to permit the location of the arms 59 close to the sideplates 11. Each of the arms59 is pivotally connected by a hinge pin 60 with a bracket 61 which is welded to the reinforcing beam 17 on the side wall of the scraperbowl. lt will benoted that .there is absolutely no obstruction on the innerface-.othe front apron 53 or on the inner faces of the ejector portions 22a and 22 b. This `combined with the smooth inner faces of the bowl side walls 11 comprises Va completely clean unobstructed interior wall construction for the scraper bowl. This is very desirable.

It should also be noted in Figs. land 3 `that the outer front'face of the apron is outwardly bowed. This .front referencetnurneral SGi'nFig. 3 to cylinder-58 which end 'Gib after the latter is fully extended. vThe cylinder-61a is pivotally mounted at 62 at the central portion of the beam 34. The secondary piston 61e is vpivotally mounted at `63 on -a suitable Vbracket on the ejector portion 2211. Pressure lluid is supplied to the cylinder 61a by the hydraulic system shown in Fig. 4 for extending the hoist to move the ejector to the dumping position of Fig. 3. In this manner, as vthe telescoping pistons 61b and 61e are of increasingly smaller diameter and the uid supply to the hoist is substantially constant, the ejector moves progressively faster as it dumps the load. This is a single acting hoist and moves the ejector to a position shown'in Fig. 3 where the center of gravity of the ejector is forward ot a vertical plane through the hinge pivot 27. Two long helical springs 64 are secured between the ejector portion 22h and suitable brackets connected to the side plates 11 just above beam 33 or 34 and the ends of beam 14. These springs lie substantially upon beam 14 when the ejector is in the position of Figs. l and 2. These springs 'are sufficiently loaded when the ejector is in the .position of Fig. 3 to cause the vinitial movement of the ejector in a clockwise direction from the position of Fig. 3 when the pressure iluid is released from the cylinder 61a. The springs 64 will return the ejector to the position whereits center of gravity lis to the rear of a vertical plane through the hinge 27 after which gravity will return the ejector to the position of Fig. l.

Means is mounted on the pull yoke 39, or more specically on the torque tube 50 for lifting the scraper bowl and front apron. This means comprises parallel spaced hoists 65 and 66'for controlling thescraper bowl and a single hoist 67 located between them and parallel to them for lifting the front apron. Each of these hoists is of similar construction and therefore one only will be explained in detail. For instance, the hoist 65 comprises a cylinder 65a which is closed at its rear end by a plate 65b which in turn is suitably secured by welding or bolting the same to a vertical plate 68 which forms a portion of a sheave housing which is mounted on the torque tube 50 and rigidly welded thereto. The top of this housing is indicated at 69 anda plurality of partition plates v70 are welded to the top 69, to the vertical plate 68 and to the torque tube 50 providing a very strong construction. Reciprocable in the cylinder 65a is a piston 65e which carries at its front end a pulleyhead 65d. Rotatably mounted in the pulley head 65d are two pulleys or sheaves 71 and 72. Rotatably mounted in the partitions 7G of the sheave'housing'are' the sheave`73 in fore-and-att alignment with sheave 71 and the sheave 74 in alignment with sheave 72. The pulley head 66d has rotatably mounted in it the parallel sheaves 75 and 76. ln the sheave housing to the rear the sheave 77 is aligned with sheave 75 and the sheave 78 is aligned with sheave 76, these sheaves 77 and 78 being rotatably mounted in the partitions 70. A single cable 79 has one end 79a fixed in a dead end wedge socket 80 on the torque tube 50 and then extends rearwardly through the plate 68, is bent around a reversing saddlefSl carried by plate 63, then has a r-un '79h which extends forwardly and around sheave 71, run 79e then extends rearwardly and over sheave 73, a moving bight 79d then extends downwardly and around a littsaddle 82 `which is oscillatably mounted on the box beam Yl2 connected to the front end of the scraper bowl. The other end of the bight 79d then extends upwardly and around sheave 74, from which a run 79e extends forwardly and around sheave 72, a run 79]c then extends rearwardly and through plate 68 and around a reversing saddle 83 mounted on plate 68, then around a cross over saddle 84 fixed on torque tube 50, then parallel to torque tube 50 and around a second cross over saddle 85 mounted on torque tube 50, then rearwardly around a reversing saddle 86 mounted on plate 68, then run 79g extends forwardly around pulley 75, then run 79h extends rearwardly, over sheave 77, and down to produce the moving bight 791' which passes around a lift saddle 87 which is fixed on the end of box beam 12 opposite the lift saddle 82. From bight '79i the cable passes upwardly and over sheave 78, then run 79j extends forwardly and over sheave 76, then run 79k extends rearwardly and around reversing saddle 88 mounted on plate 68, from which the cable extends forwardly and downwardly to another dead end wedge socket, located at the other end of the cable 89. By this arrangement, power strokes of the piston 65e and 66e forwardly, impelled by pressure fluid, will cause an upward pull on the moving cable bights 79d and 791' causing an upward lift on the lift saddles 82 and 87, thus causing the scraper bowl to rise. Because a single length of cable is used, the action of the hoists 65 and 66 is equalized. Because of the reeving of the cable 79 over the plurality of sheaves just above indicated, the movement of the hoists 65 and 66 is multiplied greatly and gives a high lift to the scraper bowl. In one form of my device, using hoists 65 and 66 having a power travel of not over seventeen inches, I find it possible to drop the scraper blade 16 fourteen inches below the grade line established by wheels 37 and 41 or raise the same to a position twentyeight inches above this grade line, or a total of forty-two inches of bowl travel in a vertical direction. Because the bowl is hung on the traveling bights 79d and 791- of the cable 79, the scraper bowl is enabled to float as the scraper is pulled forward during a digging or dirt spreading operation. This is a valuable feature of cable-operated scraper bowls, but to the best of my knowledge, has never beenrnade possible before using relatively short lengths of cable such as I have provided in the moving bights 79d and '7911 At the same time, I have as much power applied to lifting the bowl as would be found in a known type of cable-operated scraper utilizing a three-drum winch. In my case, the operating mechanism is very much simpler but provides all of the advantages of a iloating scraper bowl.

The hoist 67 is mounted parallel to and between the hoists 65 and 66 for the purpose of operating the front apron 53. This hoist consists of a cylinder 67a which is closed at its rear end by the plate 67b which in turn is bolted to the plate 68. A piston 67C is reciprocatable in the cylinder 67a by means of pressure uid supplied t0 the rear end of the cylinder. The free end of the piston carries the head 67d in which are rotatably mounted three sheaves in parallel relationship, namely, 89, 90 and 91. Aligned with these in the sheave housing are the respective sheaves 92, 93 and 94 which are rotatably mounted in the partition plates '70. A cable 95 has one end 95a secured rrnly at a dead end wedge socket 96 which fis secured in the sheave housing. A run of the cable 95b then extends forwardly and around the pulley 89, then run 95e extends rearwardly and around pulley or sheave 92, then run 95d extends forwardly around sheave 90, then run 95e extends rearwardly and around sheave 93, then run 95;c extends forwardly and around sheave 91, then run 95g extends rearwardly and around sheave 94, after which the free end of cable 95 extends downwardly as indicated at 95h and is Vsecured to an eye 96 located on the lower mid central portion of the front apron 53. It results from this construction, that when the piston 67e makes a power stroke forwardly impelled by pressure fluid admitted to the rear end of the cylinder 67a, the sheaves 89, 9i) and 91 are carried forwardly causing a pull on the cable 95 which raises theapron 53 from the closed position of Fig. 1 to the open position of Fig. 3.

It will be obvious from a study of Figs. l and 3 that the movement of the front apron 53 along with the cable 95 is in equal increments during the first half of the movement of the apron upwardly because the cable lies at against the front face of the apron 53 during this portion of apron movement. Raising cable 95 at an approximately uniform speed will raise the apron at an approximately uniform angular speed as long as cable 95 engages the lower end of the uper portion of the apron front face at reference numeral 56 in Fig. 3. After the bracket 96 passes the point of tangency with the cable 95 indicated at 97 in Fig. 3 when cable 95 disengages from said lower end of the upper portion of the apron front face, as the bracket 96 moves upwardly from the point 97, a given increment of lengthwise movement of the cable 95 at approximately the same uniform speed causes a faster angular speed or a greater increment of front apron movement while the cable 95 is moving from a position of tangency to the path of the bracket 96 to a position alrnost radially of this path of movement. For instance, as viewed in Fig. 3, the cable portion 95h is almost in line between the top of pulley 94 and the pivot point 60 about which the front apron moves. Thus, as the apron moves upwardly its speed increases although the power applied to it will decrease slightly. This is in accordance with the necessities of the case because the load on the apron is less as it reaches its raised position.

The above described apparatus for operating the front apron 53, has an advantage similar to that described in connection with the scraper bowl, namely, that the front apron floats on the relatively short length of cable 95h while the scraper is being filled but without any great length of cable to become snarled up. At the same time, the multiplication of movement through the plurality of sheaves operated by the hoist 67 gives a great deal of cable travel for the operation of the front apron.

The hydraulic system for operating the Various hydraulic hoists heretofore described is shown diagrammatically in Fig. 4. The ejector hoist cylinder 61a is connected by line 98, with valve 99 mounted on the tractor body. The two hoists 65a and 66a have their cylinders connected by lines 100 and 101 respectively with line 102 which leads to control valve 103 on the tractor body. The apron hoist 67a has its cylinder connected by line 104 with control valve 105 on the tractor body. These valves are located in a position where they may be operated by valve operating handles 99a, 10351 and 105:1 respectively located alongside the drivers seat 106 on the tractor. This is a very simple hydraulic system and one which is easy to keep in eilicient operation. Each. of the hoists is single acting. As mentioned previously, the springs 64 cause the initial return movement of the ejector from its raised position after which gravity causes the pistons 61h and 61e to return into the cylinder 61a. Obviously, the scraper bowl 12 moves downwardly under the action of gravity and the front apron 53 also returns from raised position to its lower or closed position under the action of gravity. This system makes it very easy to determine where leakages occur. For instance, if the scraper bowl tends to drift downwardly, if there is a leak in the hoist the oil will be leaking out of it and it will be simple to locate the trouble. If not, the only other place that this trouble could occur would be in the valve 193 so that the mechanic would immediately known where to go to work. Similar considerations apply `to the ejector hoist and the front apron control hoist. It will be noted also that only three exible hoses, namely, 9S, 102 and 104, are necessary between the tractor and the trailer. By mounting the valves and their control levers on the tractor, it is possible to arrange the control levers so that they are very convenient for the tractordriver to operate them.

The operation of my improved scraper should now be obvious. With the tractor moving forwardly, the operator actuates valve 103 to remove all pressure fluid from the hoists 65 and 66, thus allowing the scraper bowl to 7 drift downwardly until the blade 16 digs into the earth. At lthe same time, the operator actautes valve 105 to op- -erate hoist `67 to open the front apron 53 sufficiently to `operate the scraper .bowl to fill as desired. As the bowl `fills, the operator will eventually release all pressure fluid from the hoist 67 allowing the apron 53 to float until it reaches the closed position of Fig. l. Depending upon the type of digging, the operator may lift the scraper bowl as it fills, or he may lift it after it becomes completely yffilled. In any case, eventually the operator actuates the hoists 65 and 66 to cause the scraper bowl to be lifted to the carrying position of Fig. l. The operator then runs the tractor to the desired location, after which he operates .the hoist 67 to lift the front apron 53 and actuates the valve 99 to send pressure lluid to cylinder 61a so as to move the ejector from the position of Fig. l to the position of Fig. 3 to dump the load. Usually, during such a dumping operation the tractor and scraper are mo-ved forward so as to distribute the load in the desired manner. After the load is dumped, pressure is removed from the ejector cylinder 6in, permitting the ejector to return 'to its position in Fig. l and generally also closes the front apron 53 so as to move the scraper back to its -original position again.

One of the advantages of my improved scraper is that the mounting of the three hoists 65, 66 and 67 on the top of the pull yoke or draw bar helps through the dead weight of the scraper forward, getting more of the scraper vweight on the tractor drive wheels. in an actual test where the total tractor weight was 18,200 pounds and the scraper weight (unloaded) was 22,30() pounds, there was a slightly greater load on the drive wheels 41 than on the rear scraper wheels 37 in the unloaded condition.

`When this equipment was loaded with 42,000 pounds of earth, the actual weight on the driving tires il was 35,505 pounds and the actual weight upon the rear wheels 37 of the scraper was 36,000 pounds. This will be recognized by those skilled in the art as a very .exceptional distribution of the weight and one which is very favorable to a high traction on the rear wheels of the tractor.

As has been mentioned previously, in this same embodiment of my invention, it is possible to obtain forty-two inches of vertical travel of the bowl which is very important when an operator has to lift himself out of trouble as when the equipment has so much material piled up in front of it that it cannot move. The bottom of the front apron 53 in the position of Fig. 3 is about six feet from cutting edge 16. This helps when dumping a large mass of sticky soil.

Referring to Fig. 3, it will be noted that there is a space indicated by the dimension A between the lower side of the three hoists 65, 66 and 67 and the top of the torque tube 50. In an actual embodiment, this dimension A is about six inches and gives a clear vision of the operator. sitting on the seat of the tractor` toward the rear. This is -very important if the operator is to watch the loading of the scraper and if he is to watch a pushing tractor acting upon the bumper 3l'. The plate is cut away at its -mid portion as indicated at 63 to give clearer vision.

Another feature of my scraper is the open top of the scraper bowl. It will be noted Ythat this is unencum bered by any beams, pulleys. projections or obstructions of any sort and this is Vvery advantageous if the scraper is loaded by means of a shovel.

yThe position of the cutting blade 16 is such that the reaction of the digging or scraping operation rearwardly on the blade 16 is transferred, because of the proper location of the pivot 52, in an economical manner to cause a downward load on drive tires 4l. This greatly aids in the loading action of the scraper and particularly when there is very little dirt loaded into the scraper bowl. In other words, at the beginning of the digging action, the `drive wheels 4 1 are loaded just when the load is most needed.

Referring tto Fig. 1, it will be `noted that the pinf43 which is the pivotal connection `between the scraper and the 'tractor is located forwardly of a `plate B extending through the .axis of the axle housing 42 on which the drive wheels 41 are mounted. It is well known thatwhen a tractor is trying to `pull and unable to make progress, thefront end of the tractor tends to rear. In other words, there would be a tendency for the pivot 43 to tend to move inthe direction of the arrow of Fig. 1. It will be obvious that this movement is impossible because the entire load of the front portionof the scraper is acting downwardly at this point and must be lifted before the tractor can rear. This torque load transfer of the tractor'drive wheels provides more tractive effort for loading power inthe combinationof the tractor and the scraper.

It will be noted also that the scraper has an extremely low over-all height and extremely low center of gravity. This gives a very good stability of the scraper either empty or loaded. The scraper is very rugged and sturdy and of extreme simplicity and closely coupled to the tractor in front of it. Added to all this is a positive, fast and quickly responsive control of the working actions of the various operations of the scraperparts as described in connection with the description of the operation of my invention.

What I claim is:

l. In the combination of a digging and carrying scraper and a tractor for moving the same, a scraper bowl having side walls and a bottom and an open front end and means for closing the same, wheel means supporting the rear end of said bowl, a drawbar havinga pivotal connection between its rear end and said bowl, a hitch connection between the front end of said drawbar and said tractor, said means for closing the .front end of said bowl comprising an apron mounted .for movement up andA down, comprising .a hoist having relatively movable cylinder and piston members with one of said hoist members being fixed on said drawbar, the other member being movable generally away from said apron, comprising sheave means carried by eachof said hoist members, and comprising a cable operatively connected at one end to said hoist and reevedl over all ofsaid `sheave means to provide a movable run with said .cable operatively connected to said apron to lift the latter.

2. In the combination of a digging and carrying scraper and a tractor for moving the same, a scraper bowl having side walls and a bottom and an open front end, an apron for closing said front end and having a pivotal mounting on said bowl-for movement between a closed and an open position, wheel means supporting the rear end of said bowl, a drawbar having a pivotal connection between its rear end and said bowl, a hitch connection between the frontend of said drawbar and said tractor, a hoist having relatively movable cylinder and piston members, one of said hoist members being fixed on said drawbar, the other of said hoist lmembers being movable forwardly therefrom, a head carried by said movable hoist member, a plurality of sheaves rotatably mounted in said movable head, a xed head positioned in rear of said Xed hoist member, a plurality of sheaves rotatably mounted in said fixed head and in fore-and-aft alignment with said movable head sheaves, the axes of all of said sheaves being at right angles tothe direction of sheave reciprocation and .a cable reeved over said fixed vand movable sheaves and having a movable run thereof attached to said apron for lifting the latter upon hoist reciprocation.

3. In the combination of a digging and carrying scraper and a wheeled supporting means for supporting the vfront end thereof, a Ascraper bowl having side walls and a bottom and an open front, an apron movable up and down for opening and closing said open front, a drawbar connected to said bowl and having its front end adapted'to .connect to said wheeled supporting means, hoist means for lifting said apron, a cable connection from said hoist means to said apron for lifting the latter, said apron being mounted on a pivotal axis xed to said bowl side walls and having an outwardly bowed front face with an upper and lower portion, at least the upper and lower ends of said upper portion being located approximately the same radius from said pivotal axis for oscillation in the sarne arc about said axis when said apron is raised and lowered, said cable connection comprising a length of cable connected to said apron lower portion below said lower end and adjacent the apron lip at a smaller radius from said pivotal axis, said cable extending upwardly to said hoist means and generally tangentially to said arc while engaging said upper and lower ends when said apron is in its lowered position, so that raising said cable at an approximately uniform speed will first raise said apron at an approximately uniform angular speed as long as said cable engages said lower end while extending approximately tangentially to said arc of said lrst named radius and second raise said apron at an accelerating angular speed by decreasing the radius of pull about said pivotal axis after said apron is raised until said cable moves out of tangency with said arc, then the angular speed accelerates as the radius of pull decreases from said firstapproximately equal lengths of taut cable extend along said upper and lower portions when said apron is in closed position, whereby the apron has a uniform raising speed when resistance is great, has an accelerating raising speed as the resistance is reduced and has a high lift for rapid bowl loading and unloading.

References Cited in the le of this patent UNITED STATES PATENTS Hoar Oct. 23, 1945 Daniels Aug. 12, 1947 Reischl July 17, 1951 Hyler Aug. 28, 1951 Murray Sept. 4, 1951 Adams Apr. 13, 1954 

